How to De-restrict a Derbi Atlantis or GP1

An informative article for you do-it-yourselfers.

Derbi De-restriction
Right out of the box, the Derbi Atlantis and the Derbi GP1 are limited to a max speed of about 28mph.

On the Atlantis, the factory has installed a sleeve in the header of the exhaust pipe - to limit the engine's ability to 'breathe easily'. By drilling out this sleeve, your Atlantis will produce more low-end torque and will increase its top speed to about 40mph.

To begin, remove your exhaust pipe and identify the sleeve. Find (or buy) a drill bit that matches the diameter of the sleeve and drill it out. Feel free to remove the sleeve anyway you can. We've just found that this process works very well.

NOTE: You should be aware that metal shavings will probably drop into the pipe as you drill out the sleeve. Make sure you get all of these out of the pipe before re-installing it.

That's it. Simply re-install the pipe and you've got another 8-10 mph and more torque!

On the GP1, the exhaust system has to be modified and the variator spacer (similar to Kymco re-striction techniques), needs to be removed. To modify the exhaust pipe, you first need to locate a small 'snake like' pipe extension that extends from the header pipe. This extension is 'crimped' at the end and serves to reduce backpressure. To improve performance, you need to remove this 'extension' and then block off the header. (Hacksaw it off and then crimp it an seal it. Better yet, take the pipe off, take it to ye local shop, have the extension cut off and weld the remaining piece closed! - Yet even better - replace the pipe with an aftermarket one!)